From: syzbot <syzbot+706f5eb79044e686c794@syzkaller.appspotmail.com>
To: kartikey406@gmail.com, linux-kernel@vger.kernel.org,
syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [net?] kernel BUG in pn_socket_sendmsg
Date: Tue, 21 Apr 2026 20:04:02 -0700 [thread overview]
Message-ID: <69e83aa2.a00a0220.17a17.0021.GAE@google.com> (raw)
In-Reply-To: <20260422021327.16934-1-kartikey406@gmail.com>
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in __sk_receive_skb
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz-executor150/8596 is trying to acquire lock:
ffff888039b2c8a0 (slock-AF_PHONET/1){+.+.}-{3:3}, at: __sk_receive_skb+0x1bf/0x9e0 net/core/sock.c:563
but task is already holding lock:
ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: __sk_receive_skb+0x1f1/0x9e0 net/core/sock.c:565
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (slock-AF_PHONET){+...}-{3:3}:
rt_spin_lock+0x83/0x400 kernel/locking/spinlock_rt.c:56
spin_lock include/linux/spinlock_rt.h:45 [inline]
__sk_receive_skb+0x1f1/0x9e0 net/core/sock.c:565
sk_receive_skb include/net/sock.h:2022 [inline]
phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1
__netif_receive_skb_one_core net/core/dev.c:6210 [inline]
__netif_receive_skb net/core/dev.c:6323 [inline]
process_backlog+0x5e1/0xc60 net/core/dev.c:6674
__napi_poll+0xab/0x550 net/core/dev.c:7738
napi_poll net/core/dev.c:7801 [inline]
net_rx_action+0x696/0xe00 net/core/dev.c:7958
handle_softirqs+0x1de/0x6d0 kernel/softirq.c:626
__do_softirq kernel/softirq.c:660 [inline]
__local_bh_enable_ip+0x170/0x2b0 kernel/softirq.c:302
local_bh_enable include/linux/bottom_half.h:33 [inline]
netif_rx+0xb9/0xf0 net/core/dev.c:5776
pn_send+0x62a/0x8e0 net/phonet/af_phonet.c:188
pn_skb_send+0x218/0x530 net/phonet/af_phonet.c:275
pep_indicate net/phonet/pep.c:123 [inline]
pipe_snd_status+0x1f1/0x320 net/phonet/pep.c:221
pipe_grant_credits net/phonet/pep.c:244 [inline]
pipe_do_rcv+0xf15/0x16a0 net/phonet/pep.c:433
sk_backlog_rcv include/net/sock.h:1190 [inline]
__sk_receive_skb+0x962/0x9e0 net/core/sock.c:572
sk_receive_skb include/net/sock.h:2022 [inline]
pep_do_rcv+0x685/0xaa0 net/phonet/pep.c:675
sk_backlog_rcv include/net/sock.h:1190 [inline]
__release_sock+0x2a9/0x3d0 net/core/sock.c:3216
release_sock+0x1be/0x290 net/core/sock.c:3815
pep_sock_accept+0xd47/0x11e0 net/phonet/pep.c:879
pn_socket_accept+0xc1/0x310 net/phonet/socket.c:303
do_accept+0x6ca/0x930 net/socket.c:2062
__sys_accept4_file net/socket.c:2096 [inline]
__sys_accept4+0x139/0x230 net/socket.c:2118
__do_sys_accept4 net/socket.c:2125 [inline]
__se_sys_accept4 net/socket.c:2122 [inline]
__x64_sys_accept4+0x9a/0xb0 net/socket.c:2122
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (slock-AF_PHONET/1){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3167 [inline]
check_prevs_add kernel/locking/lockdep.c:3286 [inline]
validate_chain kernel/locking/lockdep.c:3910 [inline]
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5239
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870
rt_spin_lock_nested+0x81/0x3f0 kernel/locking/spinlock_rt.c:64
__sk_receive_skb+0x1bf/0x9e0 net/core/sock.c:563
sk_receive_skb include/net/sock.h:2022 [inline]
pep_do_rcv+0x685/0xaa0 net/phonet/pep.c:675
sk_backlog_rcv include/net/sock.h:1190 [inline]
__sk_receive_skb+0x962/0x9e0 net/core/sock.c:572
sk_receive_skb include/net/sock.h:2022 [inline]
phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1
__netif_receive_skb_one_core net/core/dev.c:6210 [inline]
__netif_receive_skb net/core/dev.c:6323 [inline]
process_backlog+0x5e1/0xc60 net/core/dev.c:6674
__napi_poll+0xab/0x550 net/core/dev.c:7738
napi_poll net/core/dev.c:7801 [inline]
net_rx_action+0x696/0xe00 net/core/dev.c:7958
handle_softirqs+0x1de/0x6d0 kernel/softirq.c:626
__do_softirq kernel/softirq.c:660 [inline]
__local_bh_enable_ip+0x170/0x2b0 kernel/softirq.c:302
local_bh_enable include/linux/bottom_half.h:33 [inline]
netif_rx+0xb9/0xf0 net/core/dev.c:5776
pn_send+0x62a/0x8e0 net/phonet/af_phonet.c:188
pn_skb_send+0x218/0x530 net/phonet/af_phonet.c:275
pep_sock_close+0x2c1/0x5b0 include/linux/skbuff.h:-1
pn_socket_release+0x9b/0xc0 net/phonet/socket.c:34
__sock_release+0xb9/0x250 net/socket.c:726
sock_close+0x1c/0x30 net/socket.c:1529
__fput+0x461/0xa70 fs/file_table.c:510
fput_close_sync+0x11f/0x240 fs/file_table.c:615
__do_sys_close fs/open.c:1507 [inline]
__se_sys_close fs/open.c:1492 [inline]
__x64_sys_close+0x7e/0x110 fs/open.c:1492
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(slock-AF_PHONET);
lock(slock-AF_PHONET/1);
lock(slock-AF_PHONET);
lock(slock-AF_PHONET/1);
*** DEADLOCK ***
7 locks held by syz-executor150/8596:
#0: ffff88805a1fc638 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1029 [inline]
#0: ffff88805a1fc638 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: __sock_release+0x89/0x250 net/socket.c:725
#1: ffff888039b2dad8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
#1: ffff888039b2dad8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: pep_sock_close+0x86/0x5b0 net/phonet/pep.c:742
#2: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: __local_bh_disable_ip+0x3c/0x420 kernel/softirq.c:163
#3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#3: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: process_backlog+0x271/0xc60 net/core/dev.c:6673
#4: ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#4: ffff888034c5b720 (slock-AF_PHONET){+...}-{3:3}, at: __sk_receive_skb+0x1f1/0x9e0 net/core/sock.c:565
#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
#5: ffffffff8e3c8140 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1e0/0x400 kernel/locking/spinlock_rt.c:57
#6: ffff888034c5b7d8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: sk_receive_skb include/net/sock.h:2022 [inline]
#6: ffff888034c5b7d8 (sk_lock-AF_PHONET){+.+.}-{0:0}, at: phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1
stack backtrace:
CPU: 0 UID: 0 PID: 8596 Comm: syz-executor150 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2045
check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2177
check_prev_add kernel/locking/lockdep.c:3167 [inline]
check_prevs_add kernel/locking/lockdep.c:3286 [inline]
validate_chain kernel/locking/lockdep.c:3910 [inline]
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5239
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870
rt_spin_lock_nested+0x81/0x3f0 kernel/locking/spinlock_rt.c:64
__sk_receive_skb+0x1bf/0x9e0 net/core/sock.c:563
sk_receive_skb include/net/sock.h:2022 [inline]
pep_do_rcv+0x685/0xaa0 net/phonet/pep.c:675
sk_backlog_rcv include/net/sock.h:1190 [inline]
__sk_receive_skb+0x962/0x9e0 net/core/sock.c:572
sk_receive_skb include/net/sock.h:2022 [inline]
phonet_rcv+0x781/0xc40 net/phonet/af_phonet.c:-1
__netif_receive_skb_one_core net/core/dev.c:6210 [inline]
__netif_receive_skb net/core/dev.c:6323 [inline]
process_backlog+0x5e1/0xc60 net/core/dev.c:6674
__napi_poll+0xab/0x550 net/core/dev.c:7738
napi_poll net/core/dev.c:7801 [inline]
net_rx_action+0x696/0xe00 net/core/dev.c:7958
handle_softirqs+0x1de/0x6d0 kernel/softirq.c:626
__do_softirq kernel/softirq.c:660 [inline]
__local_bh_enable_ip+0x170/0x2b0 kernel/softirq.c:302
local_bh_enable include/linux/bottom_half.h:33 [inline]
netif_rx+0xb9/0xf0 net/core/dev.c:5776
pn_send+0x62a/0x8e0 net/phonet/af_phonet.c:188
pn_skb_send+0x218/0x530 net/phonet/af_phonet.c:275
pep_sock_close+0x2c1/0x5b0 include/linux/skbuff.h:-1
pn_socket_release+0x9b/0xc0 net/phonet/socket.c:34
__sock_release+0xb9/0x250 net/socket.c:726
sock_close+0x1c/0x30 net/socket.c:1529
__fput+0x461/0xa70 fs/file_table.c:510
fput_close_sync+0x11f/0x240 fs/file_table.c:615
__do_sys_close fs/open.c:1507 [inline]
__se_sys_close fs/open.c:1492 [inline]
__x64_sys_close+0x7e/0x110 fs/open.c:1492
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd3c4acf98e
Code: 08 0f 85 65 e1 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 90 41 57 41 56 4d 89 c6 41 55 4d 89 cd 41 54 55 53 48 83 ec 08
RSP: 002b:00007ffcc0cf80b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 00005555771d0400 RCX: 00007fd3c4acf98e
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000077f63
R13: 0000000000077f95 R14: 00007fd3c4b6ab6c R15: 00007fd3c4b6ab60
</TASK>
Tested on:
commit: bee6ea30 Add linux-next specific files for 20260421
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=124bd702580000
kernel config: https://syzkaller.appspot.com/x/.config?x=354b135d724a721f
dashboard link: https://syzkaller.appspot.com/bug?extid=706f5eb79044e686c794
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch: https://syzkaller.appspot.com/x/patch.diff?x=17c45f16580000
next parent reply other threads:[~2026-04-22 3:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20260422021327.16934-1-kartikey406@gmail.com>
2026-04-22 3:04 ` syzbot [this message]
[not found] <20260422021207.16887-1-kartikey406@gmail.com>
2026-04-22 2:51 ` [syzbot] [net?] kernel BUG in pn_socket_sendmsg syzbot
2026-04-21 23:16 syzbot
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